Influence of rice husk ash (RHA) with gypsum and ichu fibers in the processing of geopolymers

Cement production consumes enormous amounts of fossil fuels, generating significant CO₂ emissions, seriously impacting the environment, and tons of rice husk ash (RHA) are generated annually as a result of energy production activities, much of which goes unused and is deposited in landfills, causing serious environmental damage. The present research aims to study the mechanical and microstructural properties of geopolymer with RHA, gypsum and ichu fiber, with alkaline activators of sodium hydroxide and sodium silicate. Geopolymers at 8, 10, 12 and 14 molar of sodium hydroxide with proportions of 10, 20, 30, 40 and 50% of gypsum and 0.5, 1.0, 1.5 and 2.0% of ichu fiber were elaborated and subjected to mechanical strength and microstructure analysis. The results revealed that the best combination was 12 molar with 20% gypsum and 1.5% ichu fiber, with compressive, flexural and tensile strengths of 9.72, 7.99 and 2.25 MPa; respectively, SEM images showed the generation of a large amount of geopolymeric products by the reaction of OH with the aluminosilicate components of the RHA in an alkaline source. XRD shows as crystalline phases albite, quartz, orthoclase, aphthalite and also amorphous crystalline phase. FTIR spectra showed related to H–O–H and O–H stretching vibrations of broad bands around 3450 cm⁻¹, thermogravimetric analysis shows that the residual mass at the end of the test at 990 °C is 90.6%. It is concluded that sodium hydroxide, sodium silicate together with RHA, gypsum and ichu fibers can be used as reactive materials to produce geopolymers with good mechanical characteristics.